make the log of notification about LE more readable

the log of notification about LE is very important to help us to see the process of LE:e.g.

2019-01-01 16:29:27,494 [myid:2] - INFO [WorkerReceiver[myid=2]:FastLeaderElection@595] - Notification: 1 (message format version), 3 (n.leader), 0x60b3dc215 (n.zxid), 0x3 (n.round), FOLLOWING (n.state), 1 (n.sid), 0x7 (n.peerEpoch) LOOKING (my state)

the current log have some problems:
1:don't use the placeholder(other:+),don't in the style of k:v（antiman）
2.the properties in the logs are very messed(no group by,no order), not easy to read.
3.the value about version is HEX which don't have the 0x prefix.